This invention is directed to a method for preserving the color and texture of vegetable pasta produced from alimentary pastes.
The terms "alimentary pastes" and "pastes", as used herein, refer to the flour and water mixtures which when cooked are commonly known as pasta, such as spaghetti, macaroni, noodles, ziti, etc. Alimentary pastes are generally made from coarse, hard flours obtained from hard wheat such as the middlings of durum wheat, often referred to as "semolina flour" or "semolina". Semolina comprises a major portion of the flour in alimentary pastes because it is highly glutinous and provides a self-supporting pasta. Shaped products made therefrom will substantially maintain their original form after subsequent processing, such as cooking. The term "cooking", as used herein, refers to the process of gelatinizing the starch and denaturing the protein to form a firm, rigid matrix within the alimentary paste, which occurs upon heating the alimentary paste. The term "alimentary vegetable paste" as used herein refers to alimentary pastes as defined above wherein ground, shredded, chopped or whole vegetable is included. The vegetables whose color is preserved by the method of the present invention include chlorophyll-containing vegetables such as spinach, celery, parsley, peas, and the like.
Pastas are commercially available in many forms including cooked, partially cooked and uncooked forms. "Cooked pasta" is defined herein to mean pasta wherein substantially all of the starch is gelatinized. "Uncooked pasta" is defined herein to mean pasta wherein a major portion of the starch is ungelatinized, i.e., greater than about 80% by weight of the total starch content is ungelatinized. The term "uncooked pasta" includes pasta wherein none of the starch is gelatinized. Starch gelatinization is generally accompanied by protein denaturation. Although protein denaturation is of greater concern, starch gelatinization can be quantified with greater accuracy and is therefore used herein to define cooked and uncooked pasta.
There are advantages to each of these types of pasta products; however, the most common form of pasta purchased retail is dry and uncooked pasta. This form is the most versatile because the product may be stored at room temperature for long periods of time. In addition, pasta in this form maintains its highly glutinous properties in that a substantial portion of protein is undenatured, providing a firm pasta upon cooking. Partially cooked and cooked pastas provide the advantage of rapid preparation but often require special packaging, exhibit reduced firmness and product quality, and often have a shorter shelf life than uncooked pasta.
Processes for the commercial manufacture of dry, uncooked pasta are well known. In these processes, water and semolina flour are mixed within an extruder to provide the aIimentary paste. This paste is forced through holes in the extruder die at a high pressure and at an elevated temperature, to obtain the desired cross-sectional shape. The extrudate is often cut to desired lengths. In a conventional pasta extrusion process, the alimentary paste exhibits a moisture level of about 30 weight percent and is maintained at a temperature of about 120.degree. F. (49.degree. C.).
Drying is a time consuming step in the preparation of uncooked pastas. The extrudate generally has a moisture level of about 28 weight percent or above which must be reduced to a value of about 12%-14% to permit storage of the product at ambient conditions. The drying step, or steps, may require from about 18 to 36 hours.
The addition of flavoring and/or coloring agents to pasta has in the past resulted in a pasta product with a starchy, gummy texture and which does not retain its color on shelf aging or when cooked in water. A method of preserving a color in alimentary pasta is therefore desirable.
While cations and/or high pH have been used to stabilize chlorophyll (the coloring agent in green vegetables) in canned or frozen vegetables, the use of high pH, with and without supplemental cations, in color and texture preservation in vegetable pasta is unknown.
Traditionally, the pasta industry manufactures vegetable pasta, such as spinach pasta products, from semolina and spinach powder. Spinach pasta, for example, prepared in this manner possesses a yellow-green to yellow-brown color.
Segner, et al., U.S. Pat. No. 4,473,591 issued Sept. 25, 1984, discloses a process for retaining the natural green color of canned or frozen vegetables. The green vegetables, such as spinach, are subjected to a blanching operation at 150.degree.-212.degree. F. in an aqueous solution which contains 50-500 ppm of zinc or copper ions. Once the vegetables in Segner, et al. are blanched, the vegetables are packed in a container or frozen.
Malecki, U.S. Pat. No. 2,906,628 issued Sep. 29, 1959, discloses a method of preserving the green color of vegetables. In this patent, the green color of the vegetable is preserved if immediately before or immediately after blanching, the vegetables, specifically peas, are briefly dipped in an alkaline solution, such as sodium hydroxide. It is noted that the change of color in the peas is reduced if the canning solution is maintained at a pH in the order of 8-8.5. Further, the inventor therein notes that in his co-pending application, the peas are first blanched by soaking them in a hot water bath containing magnesium hydroxide for two to five minutes. The cans are then filled with the peas and an aqueous canning solution which contains disodium glutamate and sodium hydroxide to bring the pH of the solution after processing to 8.5.
Hekal, et al., U.S. Pat. No. 4,478,860 issued Oct. 23, 1984, discloses a process for improving the organoleptic properties of canned green vegetables. Vegetables are first blanched in an alkaline solution having a pH of at least 11. The blanched vegetables are suspended in a brine having an alkalinity of between 25 and 75 milliequivalents of hydroxyl ion.
Gupte, et al., Food Technology, October 1964, discloses a method to retain more chlorophyll and, therefore, more color in spinach puree. Spinach puree was adjusted to pH 8.5 with magnesium carbonate and processed at 300.degree. F. The spinach puree retained approximately 25% of the chlorophyll after six months at room temperature.
Japanese patent No. 60-58033 published September 9, 1983, discloses a process for preparing dried vegetables. Vegetables such as spinach are blanched in an aqueous solution of pH 7-10 containing magnesium ions, and are then dried.
Japanese patent No. 60-164447 published June 2, 1984, discloses spinach-containing noodles. The noodles are prepared by adding liquid-state spinach containing sodium chloride to flour and eggs.
Regarding the art of preserving green color in canned foodstuffs, see also U.S. Pat. No. 2,305,643, issued Dec. 22, 1942 to Stevenson, et al; U.S. Pat. No. 2,189,774, issued Feb. 13, 1940 to Blair; and U.S. Pat. No. 2,589,037 issued Mar. 11, 1952 to Bendix, et al.